We are aware, from the prior art, via documents U.S. Pat. No. 4,491,927, U.S. Pat. No. 5,848,485, U.S. Pat. No. 6,336,077, U.S. Pat. No. 6,609,315 and FR 2 620 148 for example, of many systems to control the position of a tool placed at the end of an articulated arm, using inclinometric sensors communicating with a centralised electronic processing unit (generally installed in the control cabin).
We are also aware, via document US 2006/243180, of a system to classify an operation executed by a digging machine. The system can include sensors, cabled or not, positioned on the machine, with each sensor being configured to detect one or more parameters associated with the machine. In addition, the system can include a memory used to store classification data associated with different types of operations that can be executed by the machine. The system can also include a processor that is configured to receive a signal that indicates at least one detected parameter and to classify an operation on a machine in at least one of the different types of operations that can be executed by the machine as a function of the signal received and of the classification data stored.
Document US 2006/085118 also proposes an excavation machine that includes an arm, a bucket, a lift cable by which the bucket is suspended from the arm, and a drawing cable to draw the bucket. The technical means are used to supply data on the alignment, in a vertical plane containing the axis of the arm, of at least one of the components of the machine. These data can be entered via a man-machine interface by which the monitoring stage is effected by an operator, and/or it can be entered via means to monitor the control of the lift cable and/or of the drawing cable so as to reduce or stop the said control in response to the incorrect alignment detected on the components of the machine.
Document DE 43 35 479 proposes a method for detecting inclination based on the use of a measuring cell mounted on an excavation tool or digger. The inclination is measured continuously in the X and Y directions by the measuring cell. The information is stored and transferred wirelessly to a base station that relates the data item to the measured depth of the tool. The combined data are represented in a central data monitoring device and is submitted to an evaluation computer. The data item stored in the measuring cell is transferred to the base station when the cell passes through an absolute zero point.
Monitoring of the actual digging depth by the tool is a highly prized asset in the excavation field. Digging precision and rapidity can be achieved even in difficult visibility conditions. However, one drawback of these systems is pulling out of the cables connecting the sensors to the processing unit. After the breakage of a cable, the system is inoperative, since one is no longer collecting position signals from the sensor or sensors. It is therefore necessary with such systems to arrange for replacement cables and the operators have to waste time replacing the cables.
Strong protective sheathing can also be used to cover the cables or electrical connections, so as to limit instances of pulling out. Nevertheless, the use of strong protective sheathing (in stainless steel) does not prevent the pulling out of the cables in difficult digging conditions.
Another drawback of the existing systems is that it is necessary to spend at least a half day installing the set of sensors. In fact it is necessary, for example, to mount the sensor or sensors with screws, at a precise position on the arm (such as to a plate welded onto the arm for example). The protective sheathing, the electrical power cables of the sensors, and the communication cables for the position signals generated by the sensors, must also be suitably mounted. The installation of these cables (with or without sheathing) also wastes time. There is therefore a need for systems that are quicker to install and more robust in order to resist severe working conditions.